Discordant phenotypic variation in sympatric resident and anadromous Atlantic salmon (salmo-salar) populations

Sympatric but electrophoretically distinguishable resident and anadromous Atlantic salmon (Salmo salar) populations from Little Gull Lake, Newfoundland, were compared for meristic and morphometric variation. No morphometric differentiation was detected. As the two populations have similar juvenile rearing habitats, this result is consistent with the hypothesis that local water-flow conditions are important in determining morphometry. Meristic divergence is as great as that between regional North American stocks, and the Little Gull Lake resident population is significantly different from all other Newfoundland–Labrador populations. With our data we cannot separate environmental from genetic contributions to the mersitic divergences because spatially separate spawning locations coincide with temperature differences. Our results suggest that meristic, morphometric, and electrophoretic variation are likely to be congruent only by coincidence among Atlantic salmon populations and that these characteristics likely evolve independently.